This tape is a computer readable version of the Toxic Initial Inventory. For a complete understanding of the data contained on this tape it is necessary to read the introductory material in the hardcopy version. This description will only touch on a few important points. The inventory lists approximately 45,000 chemical substances in commerce in the United States. It is not a list of toxic chemicals; toxicity was not a criterion used in compiling the list. The tape consists of two major sections. The first section is the inventory, and is a listing of each substance with its CAS Registry Number, preferred name, and molecular formula where appropriate. The second section is an index to the first by synonymous names. Because of possible ambiguities in synonyms, this section must not be confused with the inventory itself. The presence of a name for a substance on this second section is not a guarantee that this substance is on the inventory. Reference to the first section is always necessary.